Chronic spine pain has been dealt with recently using improved, implantable medical devices. One set of such implantable medical devices includes implantable electrical stimulation leads. Such electrical stimulation leads can be inserted through the skin, through the ligamentum flavum, and into the epidural space or epidural potential space. The lead can then be run along the spinal cord, over the dura membrane, without puncturing the dura membrane. The electrical stimulation lead can then be advanced to a particular position in the epidural space, carefully positioned over the proper location along the spinal cord. The proper location can be determined by the implanting physician using fluoroscopy and interaction with the patient.
In some procedures, with some leads, one or more of these several surface electrodes of the lead are utilized while other surface leads are not utilized. Again, the electrode selection can be determined through interaction with the patient. When the patient's pain is masked, the lead is in the proper position and the proper electrode or electrodes have been selected. This placement procedure can be rather time-consuming. With the proper surface electrodes selected and connected to the proper end connectors, the lead can be connected to an electrical signal generator and/or sensing device.
It is highly desirable that the lead, once placed, remain in place. The lead is preferably not dislodged during the remainder of the surgical procedure. Often, a suture is used to anchor an intermediate part of the lead to the body. The lead also preferably remains in place during all subsequent physical activity by the patient. Longitudinal displacement of the lead can move the surface electrodes, making them bear on a different portion of the spinal cord, no longer masking the pain. A transverse or side to side movement of the lead can have the same effect, and can also move the surface electrodes further from the spinal cord, weakening the signal, and/or requiring greater power to reach the spinal cord. Increased power consumption can decrease battery life, which may require more frequent surgical replacement of the implanted battery.
Advancing the lead through the ligamentous structures and into the epidural space can prove difficult with some patients in some procedures. Often, a stiffening member or stylet is positioned within the lead during the insertion procedure and later removed. The stylet is typically very thin, adapted to fit within a small lumen of the rather small diameter lead. This stylet may buckle during the implantation procedure. Using a stiffer member to implant the lead might prove advantageous.
What would be advantageous are methods and devices for placing the spinal stimulation lead closely along the center of the spinal cord, and also for maintaining the side to side and longitudinal position of the lead after the initial correct placement by the treating physician.